1. CHAPTER 10 Knee

2. Introduction
Is the largest joint in body; frequently injured because it is positioned between two long bony levers

3. Bones Femur Tibia Fibula Tibial tuberosity
Recommend inserting Figures 10-3 or 10-4

4. Bones Patella Largest sesamoid bone in body Multiple functions:
Increase internal moment arm of quadriceps
Centralize force of quadriceps pull
Reduce tendon and friction forces
Contribute to overall knee stability
Provide bony protection
Bones

5. Joints Tibiofemoral (knee) Largest joint in body Hinge/ginglymus
“trocho-ginglymus”?

6. Tibiofemoral—menisci
Joints
Tibiofemoral—menisci
Wedge shaped—thickest toward outer rim
Move anteriorly with knee extension, posteriorly with knee flexion
Functions:
Deepen socket and improve congruency
Absorb and distribute forces/increase surface area

7. Tibiofemoral—menisci
Joints
Tibiofemoral—menisci
Functions:
Promote lubrication of joint
Prevent joint capsule from intruding into joint space
Partially protect against excessive motion

8. Tibiofemoral—collateral ligaments
Joints
Tibiofemoral—collateral ligaments
Origins are offset superiorly and posteriorly
Causes the collaterals to tighten with knee extension

9. Tibiofemoral—collateral ligaments
Joints
Tibiofemoral—collateral ligaments
Lateral collateral ligament
Has distinct structure—rope- or cord-like
Is located outside of joint capsule—”extracapsular”
Provides primary restraint when the knee is subjected to laterally directed forces

10. Tibiofemoral—cruciate ligaments
Joints
Tibiofemoral—cruciate ligaments
Intracapsular; extrasynovial
Named by appearance of “cross” they create
Maintain near same length throughout range of motion (ROM)

11. Tibiofemoral—cruciate ligaments
Joints
Tibiofemoral—cruciate ligaments
Anterior cruciate
Anterior medial–posterior lateral bundles
Resists anterior translation of tibia on femur
Posterior cruciate
Anterior lateral–posterior medial bundles
Resists posterior translation of tibia on femur

12. Tibiofemoral—osteokinematics (sagittal)
Joints
Tibiofemoral—osteokinematics (sagittal)
Flexion
On average, to 135°
Limited by soft tissue approximation
Extension
To 0°; often hyperextends but not past 15°
Limited by capsular tightening

13. Tibiofemoral—osteokinematics (transverse)
Joints
Tibiofemoral—osteokinematics (transverse)
Axial rotation
Occurs when knee is flexed
At 90° of flexion, 45° total (2:1; lateral:medial)
Occurs about a vertical or longitudinal axis
Normal end feels are firm—capsular

14. Patellofemoral—Q angle
Joints
Patellofemoral—Q angle
Females > Q angle compared with males
Genu varum—valgum

15. Muscles Knee extensors Quadriceps femoris Vastus lateralis
Vastus medialis oblique and vastus medialis longus
Vastus intermedius
Rectus femoris

16. Muscles Knee flexors Hamstrings Gastrocnemius—plantaris—popliteus
Gracilis
Sartorius

17. Functions of Knee Muscles
Knee extensors
Function to:
Stabilize—isometric
Decelerate—eccentric
Accelerate—concentric
Large and powerful muscle group
Necessary to match demands of ADLs and recreational activities

18. Functions of Knee Muscles
Knee extensors
Rectus femoris
Biarticular muscle crossing both hip and knee
Vastus medialis
VMO—fiber direction: 50–55°; stabilize patella
VML—fiber direction: 15–18°

19. Functions of Knee Muscles
Knee flexors
Hamstrings
Little force required by these muscles in open chain
Closed chain—great forces required particularly at hip
Dynamically restrain anterior tibial translation
Function to assist and decelerate rotation

20. Functions of Knee Muscles
One and two joint muscles acting at the knee
Majority of muscles that cross knee are biarticular.
Multijoint muscles:
Are more efficient
Produce motion in multiple planes
Seldom act at both joints simultaneously

21. Functions of Knee Muscles
One and two joint muscles acting at the knee
Knee flexion with hip extension
Hamstrings—active insufficiency
Rectus femoris—passive insufficiency
Knee extension with hip flexion
Hamstrings—passive insufficiency
Rectus femoris—active insufficiency

22. Functions of Knee Muscles
One and two joint muscles acting at the knee
Knee flexion with hip flexion
Hamstrings—elongated at hip; shortened at knee
Rectus femoris—elongated at knee; shortened at hip
Knee extension with hip extension
Hamstrings—elongated at knee; shortened at hip
Rectus femoris—elongated at hip; shortened at knee

23. Joint Forces Tibiofemoral Forces across joint increase with activity.
Shear stresses (A-P) are also experienced with knee range.
Anterior cruciate ligament (ACL) and hamstrings restrict anterior tibial translation.
Posterior cruciate ligament (PCL) and quadriceps restrict posterior tibial translation.
Excessive forces over time may promote degenerative joint disease.

24. Torque of muscles acting at knee
Joint Forces
Torque of muscles acting at knee
Hamstring/quadriceps ratio
Established with isokinetic dynamometry
Typically quantified at 60°/second during a concentric contraction of both muscle groups
Normal ratio—2:3, or 66%